In recent years, in view of social requirements for low fuel consumption and low exhaust emission, a hybrid vehicle having an engine and a motor generator (MG) as a vehicle power source attracts attention. In the hybrid vehicle, for example, as disclosed in JP-A-2009-179208, a power output device to transmit engine power and MG power to a driving shaft of the vehicle is provided with a transmission mechanism and clutches. Upon crawl running of traveling in accordance with a set vehicle speed, a gear ratio of the transmission mechanism and clutch engagement status are controlled so as to operate the MG as a power generator (i.e., regeneration control to drive the MG with the power of the axle so as to charge a battery with electric power generated with the MG). Then the regeneration torque of the MG (torque in braking direction) acts on the axle, to reduce load on a friction brake device.
However, in the above-described technique, upon control of the MG to operate as a power generator (i.e., the regeneration control to drive the MG with the power of the axle to charge the battery with the electric power generated with the MG), because the clutch is controlled in a half engagement status, energy loss due to clutch slip occurs, and it is difficult to efficiently perform the regeneration control.